1. Field of the Invention
This invention pertains to compositions suitable for the treatment, removal and/or containment of paint overspray, paint particles, and/or the various nonvolatile components of paints, lacquers, enamels and the like. More specifically, this invention relates to compositions containing organic materials which can disperse and solubilize paint constituents in an aqueous medium. This invention also pertains to paint overspray treatment compositions which remain effective over prolonged periods of use on a variety of different paint formulations.
2. Discussion of the Relevant Art
Large quantities of paint of various kinds, including lacquers, varnishes, enamels, and certain specialty paints such as urethane-based paints, catalyzed two-component paints, base coat/clear coat combination paints, high solids enamels or lacquers, and the like, are used to coat finished products in industries such as automotive manufacture and the like. These paints, lacquers and varnishes are generally solvent-based; however, certain of these paints can be water-based. Some are considered low solids paints (i.e. materials containing about 20 to about 30% solids) while others are considered high solids paints (i.e. those containing above 50% solids).
These coatings or paint materials are generally sprayed onto the piece to be painted or coated in an enclosed area such as a paint spray booth. In this operation, substantial quantities of solvent and oversprayed paint are discharged into the spray booth and the air drawn therein. Paint spray booths provide a means for capturing and containing paint overspray components. The method of choice is to contain the solid overspray material components in a suitable liquid material.
Paint spray booths generally include a chamber, a duct system for passing air through the chamber, and a sump containing circulating liquid located in the bottom of the chamber which can be directionalized in the spray booth chamber to form a curtain of liquid to contact the over-sprayed paint particles and volatile organic solvents and collect portions thereof. The paint spray booth also contains a gas discharge means such as a stack for discharging excess air or gaseous material. The paint spray booth is equipped with baffles or eliminators to reduce particulate carryout to acceptable levels such that most of the solids are retained in the paint spray booth washwater.
The liquid employed in paint spray booth applications is most preferably a hydrophilic material capable of removing solid particulates from the air. The liquid chosen is ideally economical and safe to use. The hydrophilic material of choice typically is comprised of water to which various chemicals are added to provide detackifying properties. Water-based compositions are also desirable for their general ease and safe handling during operation and during spray booth clean-up and maintenance. There are several drawbacks with such water-based systems. These include inconsistent paint kill and detackification, deposits on surfaces, accumulation of paint sludge, increased wet-sludge handling and disposal, and the weak performance of water-based systems as paint dispersants or solubilizers.
In contrast to water systems, various organic solvent systems have been proposed for use in paint spray booth applications; i.e. a solvent composition employing a solvent such as n-methyl pyrrolidone as disclosed in U.S. Pat. No. 5,019,138 to Farrah and U.S. Pat. No. 4,941,491 to Goerss. In solvent compositions, problems may be encountered during other operations in the paint spray booth employing water, such as routine cleaning maintenance and fire protection. In addition, the fluid properties of the solvent are likely to cause changes in the performance of the spray booth. Thus, paint spray booths may require modifications to successfully utilize solvent-based systems. It can be readily appreciated that such measures may be cumbersome and expensive.
Heretofore, one improvement has been to employ oil-in-water formulations in which water, oil and various additives are combined to form a suitable emulsion as the hydrophilic liquid of choice. The use of such oil-in-water emulsions is taught in U.S. Pat. Nos. 4,378,235, 4,396,405, 4,523,932, 4,563,199, 4,444,573, 4,544,026, 4,750,919, and 4,919,691, all of which are incorporated herein by reference.
Oil-in-water emulsions have been employed to contain greater volumes of paint solids than contained in water alone. However, the amount contained in such compositions is generally no greater than 4-6% by volume. There is no evidence to indicate that the oil-in-water emulsions currently in use dissolve or solubilize the paint which they contact. Thus, the capacity of the emulsion is limited to its dispersion capabilities and this is generally a function of the concentration of oil. In order to be effective, oil-in-water emulsions generally contain in excess of 25% by volume oil. In large capacity spray booths, this represents a significant material handling activity as well as increased operating expense.
These oil-in-water emulsions are generally weak alkaline emulsions which are easily broken. In order to maintain the material in an emulsified state, it is necessary to employ emulsion stabilizing additives, paying close attention to composition pH, and in many instances, requiring continued mechanical agitation.
Many of the patents previously enumerated provide various approaches for addressing some or all of the shortcomings inherent in oil-in-water emulsions. Of these, U.S. Pat. No. 4,919,691 to Patzelt et al has been one of the more effective. U.S. Pat. No. 4,919,691 to Patzelt et al discloses an oil-in-water emulsion which includes a process oil, a suitable oil-in-water emulsifier; and a non-polar organic solvent chosen from the group consisting of dialkyl esters of dibasic acids (DBE) such as dimethyl adipate, dimethyl glutarate, or dimethyl succinate in combination with water. Such additives were included in oil-in-water formulations to increase paint solids capacity in the emulsion and improved paint solids recovery. However, oil-in-water formulations containing DBE have significant drawbacks. DBE readily hydrolyses to form water-soluble products which are difficult to remove from water. The products of hydrolysis consume caustic, which thereby lowers the pH of the emulsion, thus jeopardizing its already poor stability. Thus, both caustic and DBE must be replenished to ensure emulsion stability and effectiveness. This fact, and the fact that DBE is non-recoverable from the spent material, represent significant drawbacks for any program utilizing oil-in-water formulations containing DBE.
Given the problems encountered with the various hydrophilic liquids currently available, there has been some incentive for manufacturers to switch to alternative technologies for paint spray containment and recovery. However, paint spray booths generally represent major items of capital investment so that wholesale replacement would be prohibitively expensive. Thus, it is highly desirable to develop a liquid composition which performs better and overcomes some of the drawbacks attributable to the circulating fluid in existing paint spray booth systems.
In Ser. No. 08/038,011 which is currently pending, the inventors proposed a paint overspray treatment composition which is composed of a carbonyl compound selected from the group consisting of secondary alcohol esters, condensation products of secondary alcohol esters and carboxylic acid and mixtures thereof in combination with a surfactant and water. In U.S. Pat. No. 5,200,104 which is the parent application of Ser. No. 08/038,011, the inventors proposed a paint overspray treatment composition which is composed of a carbonyl compound selected from the group consisting of secondary alcohol esters, condensation products of secondary alcohol esters and carboxylic acid, and mixtures thereof in combination with an emulsifier and water. In U.S. Pat. No. 5,198,143, the inventors proposed an enhanced paint overspray treatment composition which is composed of alcohol esters, condensation products of alcohol esters and carboxylic acid and mixtures thereof in combination with an emulsifier, a surfactant and water.
It was heretofore posited that the use of organic additives such as emulsifiers or surfactants was required to ensure emulsion stability or performance. This belief was due, in part, to knowledge derived from the performance of paint overspray treatment emulsions which contained materials other than secondary alcohol esters which were unable to interact effectively with contained paint. In such systems, use of surfactants, emulsifiers or combinations of the two were required to disperse or maintain the paint in the composition. Ongoing research into the particular chemistry of secondary alcohol esters and condensation products of secondary alcohol esters with carboxylic acid has lead to the unexpected discovery that such materials have heretofore unappreciated inherent properties for interacting with paint solids to render the paint dispersible in the composition.
The ability to provide an effective paint overspray treatment solution which does not require separate surfactant or emulsifier componants is highly desirable from a standpoint of cost savings and ease of use.
It would be desirable to provide a composition which has a greater capacity for containing paint either by solubilization, dispersion, or a combination of the two. It would also be desirable to provide a stable aqueous composition in which contained paint is maintained rather than settling out freely.
It is also desirable that the aqueous composition be made up of chemically stable components which retain their effectiveness in composition for a protracted period of time and which can be readily separated and recovered from the composition when required. It is also desirable that all components in the composition be economical and safe to handle and use. Finally, it is desirable that the composition employed require lower concentrations of active ingredients to achieve effective paint containment than previously obtainable and that the paint sludge thus contained be recoverable in a form which is easy to handle and process.